Peroxides, their preparation process and use

ABSTRACT

The present invention relates to a new class of peroxides and to a process for the preparation of these peroxides having the general formula (I),                    
     wherein n=1 or 2, R 1 , R 2 , R 4 , R 5 , and R 6  are independently selected from the group comprising hydrogen, C 1 -C 20  alkyl, C 3 -C 20  cycloalkyl, C 6 -C 20  aryl, C 7 -C 20  aralkyl, and C 7 -C 20  alkaryl, or R 1  and R 2  form a C 3 -C 12  cycloalkyl group, which groups may include linear or branched alkyl moieties; and each of R 1 , R 2 , R 4 , R 5 , and R 6  may optionally be substituted with one or more groups selected from hydroxy, alkoxy, linear or branched alkyl, aryloxy, halogen, ester, carboxy, nitrile, and amido, and R 1  and R 2  may form a ring, and 
     R 3  is independently selected from the group comprising C 1 -C 20 , alkyl; C 3 -C 20  cycloalkyl, C 6 -C 20  aryl, C 7 -C 20 , aralkyl, and C 7 -C 20  alkaryl, which groups may include linear or branched alkyl moieties; and R 3  may optionally be substituted with one or more groups selected from hydroxy, alkoxy, linear or branched alkyl, aryloxy, halogen, ester, carboxy, nitrile, and amido, and any pair of the optionally substituted R 3 , R 4 , R 5 , and R 6  may form a ring, comprising the reaction of the corresponding ketone.

This is the national phase of PCT EP99/05478, filed Jul. 28, 1999, nowWO 00/09478.

The present invention relates to particular peroxides, their preparationprocess, and their use. More particularly, the present invention relatesto the preparation process of these peroxides, which are obtainable bythe reaction of a corresponding ketone peroxide and an alkyl vinyl etheror an acetal. Finally, the present invention relates to the use of theseperoxides as polymerization initiators, curing agents for unsaturatedpolyesters, and modifying agents, and to formulations comprising theseperoxides.

U.S. Pat. No. 3,576,826 discloses ether peroxy compounds and theirpreparation from alpha-substituted vinyl ether. In the class of etherperoxides (v) the adjacent peroxide groups may be separated by anunidentified aliphatic or cycloaliphatic group.

It is an object of the present invention to provide a new class ofperoxides which are useful as polymerization initiators, curing agentsfor unsaturated polyesters, and modifying agents.

It is another object of the invention to provide peroxides with a higherreactivity in view of compounds of U.S. Pat. No. 3,576,826.

It is a further object of the invention to provide peroxides with abetter storage stability at room temperature in view of compounds ofU.S. Pat. No. 3,576,826.

Accordingly the present invention provides a process for the preparationof a peroxide having the general formula (I),

wherein n=1 or 2, R₁, R₂, R₄, R5, and R₆ are independently selected fromthe group comprising hydrogen, C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀aryl, C₇-C₂₀ aralkyl, and C₇-C₂₀ alkaryl, or R₁ and R₂ form a C₃-C₁₂cycloalkyl group, which groups may include linear or branched alkylmoieties; and each of R₁, R₂, R₄, R₅, and R₆ may optionally besubstituted with one or more groups selected from hydroxy, alkoxy,linear or branched alkyl, aryloxy, halogen, ester, carboxy, nitrile, andamido, and R₁ and R₂ may form a ring; and R₃ is independently selectedfrom the group comprising C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl,C₇-C₂₀ aralkyl, and C₇-C₂₀ alkaryl, which groups may include linear orbranched alkyl moieties; and R₃ may optionally be substituted with oneor more groups selected from hydroxy, alkoxy, linear or branched alkyl,aryloxy, halogen, ester, carboxy, nitrile, and amido, and any pair ofthe optionally substituted R₃, R₄, R₅, and R₆ may form a ring,comprising the reaction of the corresponding ketone peroxide with thegeneral formula (II)

wherein n, R₁, and R₂ have the identified meaning, with an alkyl vinylether with the general formula (IIIa) or with an acetal with the generalformula (IIIb)

wherein R₃, R₄, R₅, and R₆ have the identified meaning, in the presenceof a catalyst.

The ketone peroxide of formula II may be a so-called T₄-ketone peroxide(n=1) and/or a so-called T₃-ketone peroxide (n=2).

The T₄-ketone peroxides having general formula IIa

which are suitable for the reaction with said alkyl vinyl ether offormula IIIa or with said acetal of formula IIIb are those formed fromthe following ketones: acetone, acetophenone, methyl-n-amyl ketone,ethylbutyl ketone, ethylpropyl ketone, methylisoamyl ketone,methylheptyl ketone, methylhexyl ketone, ethylamyl ketone,diethylketone, dipropyl ketone, methylethyl ketone, methylisobutylketone, methylisopropyl ketone, methylpropyl ketone, methyl-n-butylketone, methyl-t-butyl ketone, methyl cyclohexanone, isobutylheptylketone, diisobutyl ketone, methoxy acetone, cyclohexanone,3,3,5-trimethyl cyclo hexanone, N-butyllevulinate, ethylacetoacetate,methylbenzyl ketone, phenylethyl ketone, methylchloromethyl ketone,methylbromomethyl ketone; also other ketones having the appropriate R₁and R₂ groups corresponding to the peroxides of the formula II can beemployed, as well as mixtures of two or more different ketones.

The T₃-ketone peroxides having the general formula IIb

which are suitable for the reaction with said alkyl vinyl ether offormula IIIa or said acetal IIIb are those that are derived from thesame group of ketones as mentioned for the T₄-ketone peroxides.

Preferably, the ketone peroxide is formed or derived from methylethylketone, methylisopropyl ketone, methylisobutyl ketone, acetone,cyclohexanone and/or 3,3,5-trimethylcyclohexanone. Methyl isobutylketone and methyl ethyl ketone are most preferable.

The alkyl vinyl ethers of formula IIIa (in which R₄ is hydrogen) may beexemplified as follows:

vinyl 2,2-bis(vinyloxymethyl)butyl ether, allyl 2,3-epoxypropyl ether,n-propyl vinyl ether, 1-ethoxy-4-methyl-1-nonene, tert.amyl vinyl ether,2,2-bis (4-vinyloxyphenyl)propane, hexadecyl vinyl ether, methyl vinylether, 4-methylhexyl vinyl ether, 2-(2-ethoxyethoxy)ethyl vinyl ether,2-methoxyethyl vinyl ether, 2-vinyloxy ethanol, 4-methyl-1-decenyl vinylether, benzyl 1-methyl vinyl ether, butanediol divinyl ether, tert.butylvinyl ether, isobutyl vinyl ether, cyclohexanedimethanol divinyl ether,cyclohexyl vinyl ether, ethyleneglycol divinyl ether,1-ethoxy-4-(1-ethoxyvinyl)-3,3,5,5-tetramethylcyclohexene, allyl vinylether, isopropyl vinyl ether, ethyl vinyl ether, tetraethyleneglycoldivinyl ether, 1-methoxy-1-buten-3-yne, heptyl vinyl ether,4-(1-ethoxyvinyl)-3,3,5,5-tetramethylcyclohexanone, 2-butoxyethyl vinylether, allyl ethyl ether, divinyl ether,1,3-divinyloxy-2,2-dimethylpropane, 4-vinyloxybutanol, diethyleneglycoldivinyl ether, 4-(vinyloxymethyl) cyclohexylmethanol, isopentyl vinylether, diethyleneglycol monovinyl ether, n-butyl vinyl ether,1,4-bis(2-vinyloxyethyl)benzene, hexanediol divinyl ether,1-methoxy-1,3-butadiene, decyl vinyl ether,4-(allyloxymethyl)-1,3-dioxolan-2-one, 1,1-diethylpropyl vinyl ether,2-methoxyvinyl benzene, octyl vinyl ether, bis(vinyloxy)methane,1,4-dimethoxy-1,3-butadiene, triethyleneglycol divinyl ether, pentylvinyl ether, octadecyl vinyl ether, triethyleneglycol methyl vinylether, 2,3-epoxypropyl vinyl ether, dodecyl vinyl ether,1,1-bis(vinyloxy)butane, hexyl vinyl ether, 6-vinyloxyhexanol,(z)-1-methoxy-1-buten-3-yne, phenyl vinyl ether, 2-ethylhexyl vinylether, poly-THF-divinyl ether, pluriol-E-200-divinyl ether,trimethylolpropane trivinyl ether, aminopropyl vinyl ether,2-diethylaminoethyl vinyl ether, ethyl propenyl ether.

Examples of alkyl vinyl ethers of formula IIIa in which R₄ is alkyl areas follows: 2-methoxy-2 butene, 1,1,3-trimethoxypropene,2,3-dimethoxy-1,3-butandiene, 2-methoxypropene, 2-ethoxy propene,2-isobutoxypropene, 2-ethoxy-2-butene, 2-isobutoxy-2-propene.

Examples of tri-substituted and cyclic alkyl vinyl ethers are1-methoxy-2-methyl cyclohexene and 2-methoxy-2-methyl-2-butene. Examplesof the cyclic alkyl vinyl ethers are 2-methyl-2,3-dihydrofuran,2,3-dihydrofuran, 2-methyl-3,4-dihydropyran, 3,4-dihydropyran, 1-methoxycyclohexene. Preferred are ethyl vinyl ether, isobutyl vinyl ether,propyl vinyl ether, and butyl vinyl ether. Most preferred is isobutylvinyl ether.

Examples of acetals of formula IIb are 2,2-dimethoxypropane,2,2-diethoxypropane (with R₄ is alkyl) or, 1,1-dimethoxybutane,2-propyl-1,3-dioxolane, 1,1-dimethoxyethane, 1,1-diethoxyethane,1,1-diethoxypropane, and 1,1-dimethoxycyclohexane (with R₄ is hydrogen).Preferred is 1,1-dimethoxyethane.

The reaction between the ketone peroxide of formula II and the alkylvinyl ether of formula IIIa or acetal of formula IIIb is carried outunder conditions conventional for this type of addition reaction. Thetemperature generally is in the range of 0-50° C. and preferably isbetween 1-25° C. The reaction is carried out in the presence of an acidcatalyst. The amount of acid catalyst generally is 0.01-30 g/mole andpreferably 0.1-15 g/mole of ketone peroxide.

The acid catalyst for the process is a conventional acidic catalyst suchas a C₁-C₁₀ alkane or aryl sulphonic acid, a halogenated C₁-C₁₀ alkanesulphonic acid or a mixture of one or more of these compounds. Thepreferred catalysts for use are, but are not limited to,p-toluenesulfonic acid and methane sulfonic acid. Although this reactionmay be carried out without a solvent, it is preferred to carry out thereaction in a conventional homogenous solvent system.

Suitable solvents generally are hydrocarbon solvents, esters, aromatichydrocarbon solvents, aralkyl solvents, paraffinic oils, white oils, andsilicone oils, as well as their mixtures. Useful solvents include, butare not limited to, benzene, xylene, toluene, mesitylene, hexane,hydrogenated oligomers of alkanes such as Isopar^(R) products (ex.Exxon), Shellsol^(R) products (ex Shell), pentane, heptane, decane,isododecane, decalin, dibutyl phthalate, dioctyl adipate, dioctylterephthalate, 2,2,4-tri methyl-1,3-pentanediol diisobutyrate,butylbenzoate, and the like. Among the paraffinic oils useful assolvents is paraffinic diesel oil. Other oils, including white oils,epoxidized soybean oils, and silicone oils are also useful in thepresent invention.

Preferably, R₄ is hydrogen because the peroxides show a better storagestability at ambient temperature and are less sensitive to hydrolysis.More preferably, R₄ and R₅ and/or R₆ are hydrogen.

Generally, the preparation process of the peroxide is carried out suchthat an equivalent amount of the alkyl vinyl ether of formula IIIa or ofthe acetal of formula IIIb is in the range of 1-5 equivalents.Preferably, the range is from 1.5 to 3.0 equivalents, more preferablyfrom 2.0 to 2.5 equivalents. These numbers of equivalents are selectedsuch that the chemical yield is optimal.

It is noted that in the preparation process the ketone peroxide used maybe pure (T₄) ketone peroxide of formula IIa or (T₃) ketone peroxide offormula IIb. For specific properties it may be recommendable to use amixture of T₄- and T₃-ketone peroxides. For instance, the T₃- orT₄-ketone peroxide may comprise 5%-30%, e.g., 5%-25% and 10%-15%, of theother ketone peroxide.

Furthermore, the invention relates to the peroxides of formula I

wherein R₁, R₂, R₃, R₄, R₅, and R₆ have the identified meaning and whichare obtainable with the above-described preparation process.

The peroxides according to the present invention produced with thepreparation processes according to the present invention may be used asinitiators for polymer production and in particular for the preparationof poly(vinylchloride), acrylic (co)polymers, polystyrene, polyethylene,for curing unsaturated polyester resins, and for polymer modification(such as grafting of monomers).

In the present invention, the polymerization is conducted by anyconventional process, except that a specified radical polymerizationinitiator (or composition) is used. The polymerization processes may becarried out in the usual manner, for example in bulk, suspension,emulsion or solution. In the case of the production of ethylene(co)polymers, the reaction is usually carried out under high pressure,e.g. about 1000 to about 3500 bar.

The amount of initiator, which varies depending on the polymerizationtemperature, the capacity for removing the heat of polymerization, and,where applicable, the kind of monomer to be used, and the appliedpressure, should be an effective amount for achieving polymerization.Usually, from 0.001-25 wt. % of peroxide, based on the weight of the(co)polymer, is employed. Preferably, from 0.001-20 wt % of peroxide isemployed and most preferably from 0.001-15 wt. %.

For most reactions within the present invention the polymerizationtemperature usually is 30° to 350° C., preferably 40° to 300° C. Ingeneral, if the temperature is below 30° C., the polymerization timebecomes too long. However, when it exceeds 350° C., the radicalpolymerization initiator is spent in the initial stage of thepolymerization, making it difficult to attain a high conversion. Inorder to reduce the amount of unreacted monomer, however, it is alsopossible to conduct the polymerization using a temperature profile,e.g., to perform the initial polymerization at below 100° C. and thenelevate the temperature above 100° C. to complete the polymerization.These variations are all known to the man skilled in the art, who willhave no difficulty selecting the reaction conditions of choice,depending on the particular polymerization process and the specificradical polymerization initiator to be used.

Suitable monomers for polymerization using the peroxides according tothe present invention are olefinic or ethylenically unsaturatedmonomers, for example substituted or unsubstituted vinyl aromaticmonomers, including styrene, alpha-methylstyrene, p-methylstyrene, andhalogenated styrenes; divinylbenzene; ethylene; ethylenicallyunsaturated carboxylic acids and derivatives thereof, such as(meth)acrylic acids, (meth)acrylic esters, butyl acrylate, hydroxyethyl(meth)acrytate, methyl(meth)acrylate, 2-ethyihexyl (meth)acrylate, andglycidyl methacrylate; ethylenically unsaturated nitriles and amides,such as acrylonitrile, methacrylonitrile, and acrylamide; substituted orunsubstituted ethylenically unsaturated monomers, such as butadiene,isoprene, and chloroprene; vinyl esters, such as vinyl acetate and vinylpropionate; ethylenically unsaturated dicarboxylic acids and theirderivatives including mono- and diesters, anhydrides, and imides, suchas maleic anhydride, citraconic anhydride, citraconic acid, itaconicacid, nadic anhydride, maleic acid, fumaric acid, aryl, alkyl andaralkyl citraconimides and maleimides; vinyl halides, such as vinylchloride and vinylidene chloride; vinyl ethers, such as methylvinylether and n-butyl vinyl ether; olefins, such as isobutene and4-methylpentene; allyl compounds, such as (di)allyl esters, for examplediallyl phthalates, (di)allyl carbonates, and triallyl (iso)cyanurate.

During (co)polymerization, the formulations may also contain the usualadditives and fillers. As examples of such additives may be mentioned:stabilizers such as inhibitors of oxidative, thermal or ultravioletdegradation, lubricants, extender oils, pH controlling substances, suchas calcium carbonate, is release agents, colourants, reinforcing ornon-reinforcing fillers such as silica, clay, chalk, carbon black, andfibrous materials, such as glass fibers, plasticizers, diluents, chaintransfer agents, accelerators, and other types of peroxides. Theseadditives may be employed in the usual amounts.

Finally, the polymerization process of the present invention can beemployed to introduce functional groups into the (co)polymers. This maybe accomplished by employing a peroxide which contains one or morefunctional groups attached thereto. These functional groups remainintact in the free radicals formed by the peroxides and thus areintroduced into the (co)polymer. Conventional polymerization conditionsand equipment may be used to achieve this object of the presentinvention.

The peroxides according to the invention which may be used as a curingagent for the unsaturated polyesters and unsaturated polyester resinsaccording to the present invention usually include an unsaturatedpolyester and one or more ethylenically unsaturated monomers. Suitablepolymerizable monomers include styrene, alpha-methylstyrene,p-methylstyrene, chlorostyrenes, bromostyrenes, vinylbenzyl chloride,divinylbenzene, diallyl maleate, dibutyl fumarate, triallyl phosphate,triallyl cyanurate, diallyl phthalate, diallyl fumarate, methyl(meth)acrylate, n-butyl (meth)acrylate, ethyl acrylate, and mixturesthereof which are copolymerizable with the unsaturated polyesters. Theunsaturated polyesters are, for example, polyesters as they are obtainedby esterifying at least one ethylenically unsaturated di- orpolycarboxylic acid, anhydride or acid halide, such as maleic acid,fumaric acid, glutaconic acid, itaconic acid, mesaconic acid, citraconicacid, allylmalonic acid, tetrahydrophthalic acid, and others, withsaturated and unsaturated di- or polyols, such as ethylene glycol,diethylene glycol, triethylene glycol, 1,2- and 1,3-propane diols, 1,2-,1,3-, and 1,4-butane diols, 2,2-dimethyl-1,3-propane diols,2-hydroxymethyl-2-methyl-1,3-propane diol, 2-buten-1,4-diol,2-butyn-1,4-diol, 2,4,4-trimethyl-1,3-pentane diol, glycerol,pentaerythritol, mannitol, and others. The di- or polycarboxylic acidsmay be partially replaced by saturated di- or polycarboxylic acids, suchas adipic acid, succinic acid, and others, and/or by aromatic di- orpolycarboxylic acids, such as phthalic acid, trimellitic acid,pyromellitic acid, isophthalic acid, and terephthalic acid. The acidsused may be substituted with groups such as halogen. Suitablehalogenated acids include, for example, tetrachlorophthalic acid andtetrabromophthalic acid.

The peroxides of the present invention are suited for use in themodification of polymers such as degradation, cross-linking or grafting.More particularly, these peroxides can be employed in processes forgrafting monomers onto polymers such as polyolefins and elastomers, andfor the functionalization of polyolefins in the case of functionalgroup-containing peroxides of the present invention.

In general, the peroxide may be brought into contact with the(co)polymer in various ways, depending upon the particular object of themodification process.

The polymer material may be in the solid state, the molten state, in theform of a solution in the case of an elastomer, in a plastic state or inany physical form including finely divided particles (flakes), pellets,film, sheet, in the melt, in solution, and the like. Polymers may alsobe in the liquid form, e.g. liquid rubbers.

In general, any (co)polymer comprising abstractable hydrogen atoms, inparticular polyolefins, can be modified by the present process.

The amount of peroxide used in the modification process of the presentinvention should be an effective amount for achieving significantmodification of the (co)polymer when treating a (co)polymer. Moreparticularly, from 0.001-15.0 wt. % of peroxide, based on the weight ofthe (co)polymer, should be employed. More preferably, from 0.005-10.0wt. % percent is employed. Most preferably, an amount of 0.01-5.0 wt. %is employed.

The peroxides can be prepared, transported, stored, and applied in theform of powders, granules, pellets, pastilles, flakes, slabs, pastes,solid masterbatches, and liquids. These formulations may have the formof a dispersion, such as a suspension or an emulsion. They can bephlegmatized if necessary, depending on the particular peroxide and itsconcentration in the formulation. Which of these forms is to bepreferred depends partly on the application for which it will be usedand partly on the manner in which it will be mixed. Also, considerationsof safety may play a role to the extent that phlegmatizers may have tobe incorporated into certain compositions to ensure their safe handling.

The formulations of the present invention are transportable, storagestable, and contain 1.0-90 wt. % of one or more peroxides according tothe present invention. Transportable means that the formulations of thepresent invention have passed the pressure vessel test (PVT). Storagestable means that the formulations of the present invention are bothchemically and physically stable during a reasonable storage periodunder standard conditions.

Preferred formulations in accordance with the present invention contain10-90 wt. % of one or more of the peroxides, more preferably theseformulations contain 30-90 wt. % of the peroxides, most preferably theseformulations contain 40-80 wt. % of the peroxides.

The formulations of the present invention can be liquids, solids orpastes, depending on the melting point of the peroxide and the diluentemployed. Liquid formulations can be made using liquid phlegmatizers forthe ketone peroxide, liquid plasticizers, organic peroxides, andmixtures thereof as the diluent. The liquid component generally ispresent in an amount of 1-99 Wt. % of the composition, preferably 10-90wt. %, more preferably 30-90 wt. %, and most is preferably 40-80 wt. %of the liquid formulation consists of liquid diluents.

It should be noted that certain phlegmatizers may not be suitable foruse with all of the peroxides of the present invention. Moreparticularly, in order to obtain a safe composition, the phlegmatizershould have a certain minimum flash point and a boiling point relativeto the decomposition temperature of the peroxide such that thephlegmatizer cannot be boiled off leaving a concentrated, unsafe ketoneperoxide composition behind. Thus, the lower-boiling phlegmatizersmentioned below may only be useful, for example, with particularsubstituted peroxides of the present invention which have a lowdecomposition temperature.

In liquid formulations a liquid carder or diluent is used. Preferably,this carrier or diluent is a solvent. Examples of the solvents are thosegiven above for the preparation of the various peroxides.

In the solid and/or paste formulations of the present invention solidcarrier materials are employed. Examples of such solid carriers arelow-melting solids, such as dicyclohexyl phthalate, dimethyl fumarate,dimethyl isophthalate, triphenyl phosphate, glyceryl tribenzoate,trimethyl olethane tribenzoate, dicyclohexyl terephthalate, paraffinicWaxes, dicyclohexyl isophthalate, polymers, and inorganic supports.Inorganic supports include materials such as fumed silica, precipitatedsilica, hydrophobic silica, chalk, whiting, surface-treated clays suchas silane-treated clays, calcined clays, and talc.

Polymers useful in the formulations of the present invention includepolyethylene, polypropylene, ethylene/propylene copolymers,ethylene/propylene/diene/monomer terpolymers, chlorosulphonatedpolyethylene, chlorinated polyethylene, polybutylene, polyisobutylene,ethylene/vinyl acetate copolymers, polyisoprene, polybutadiene,butadiene/styrene copolymers, natural rubber, polyacrylate rubber,butadiene/acrylonitrile copolymers, acrylonitrile/butadiene/styreneterpolymers, silicone rubber, polyurethanes, polysulphides, solidparaffins, and polycaprolactone.

Storage stable formulations must be both physically and chemicallystable. By physically stable formulations are meant those formulationswhich do not suffer from significant phase separation upon storage. Thephysical stability of the present formulations can, in some instances,be improved by the addition of one or more thixotropic agents selectedfrom cellulose esters, hydrogenated castor oil, and fumed silica.Examples of such cellulose esters are the reaction products of celluloseand acid compounds selected from, for example, acetic acid, propionicacid, butyric acid, phthalic acid, trimellitic acid, and mixturesthereof.

By chemically stable formulations are meant those formulations which donot lose a significant amount of their active oxygen content uponstorage. The chemical stability of the present formulations can, in someinstances, be improved by the addition of one or more known additivesincluding sequestering agents such as dipicolinic acid and/orantioxidants such as 2,6-di(t-butyl)4-methyl phenol and para-nonylphenol.

The formulations of the present invention may also contain optionalother additives as long as these do not have a significant adverseeffect on the transportability and/or storage stability of theformulations. As examples of such additives may be mentioned:anti-caking agents, free-flowing agents, anti-ozonants, anti-oxidants,anti-degradants, U.V. stabilizers, coagents, fungicides, antistats,pigments, dyes, coupling agents, dispersing aids, blowing agents,lubricants, process oils, and mold-release agents. These additives maybe employed in their usual amounts.

The peroxides according to the invention may also be used as adispersion, preferably in a polar medium. The medium in which theinitiator according to the invention is dispersed should be inerttowards the initiator and so polar that the initiator will hardlydissolve in it. The initiator preferably is dispersed in water or analcohol. Most preferable is a dispersion in water. The use of such amedium makes for comparatively easy removal of any remnant, for exampleafter the modification of the (co)polymer if so desired. Furthermore,the use of water or alcohols is attended with far fewer organoleptic andother drawbacks than the use of organic diluents, such as toluene andxylene, which has been common up to now.

As is well-known to the skilled person, the use of other adjuvants ininitiator dispersions may be advisable or even essential in order toensure the dispersion's chemical and/or physical stability for asufficiently long period of time. For instance, if the storagetemperature of the initiator dispersion is lower than the freezing pointof the medium in which the initiator is dispersed, an appropriatefreezing point depression agent can be added to counteract freezing.Also, a wide range of substances can be used for altering the rheologyof the formulation. To this end generally use is made of one or moresurface-active materials and one or more thickeners. If so desired,other additives may be incorporated into the formulation. As examples ofsuch additives may be mentioned pH buffers, biocides, chemicalstabilizers which counteract premature decomposition of the initiator,and anti-agers which counteract particle size growth in the dispersion.

The following examples illustrate the preparation processes for theperoxides according to the present invention and their applications.

EXAMPLE 1

Preparation of a mixture of2.2.-bis(1-(1-methylpropoxy)ethylperoxy)butane andbis[1-methyl-1(1-(2-methylpropoxy)ethylperoxy)propyl]peroxide

To a stirred solution of 25 g methylethyl ketone peroxide containing27.82 wt. % 2,2-bis(hydroperoxy)butane T4 ketone peroxide and 14.4 wt. %bis(1-hydroperoxy-1-methylpropyl)peroxide T3 in dimethylphthalate wasadded 0.86 g p-toluene sulfonic acid monohydrate. Then 18.3 g isobutylvinyl ether were added in 16 min, the reaction temperature being kept at20° C. by cooling with an ice-water bath. The mixture was stirred for 2min at 20° C. washed with bicarbonate solution, and dried over magnesiumsulphate, yielding 41.6 g of product with an active oxygen content of6.33% (chemical yield: 90%).

The following Table 1 shows the results of the preparation of otherperoxides according to the invention (R₁=methyl; R₄, R₅, and R₆=H).

TABLE 1 Ex- am- n = 1:n = 2 Yield Active ple R3 R2 Mole/mol Solvent %Oxygen (%) 1a Ethyl Ethyl 56:44 Dimethyl- 87 7.04 phthalate 1b EthylEthyl 77:23 Dimethyl- 90 7.52 phthalate 1c Iso- Ethyl 56:44 Dimethyl- 916.24 butyl phthalate 1d Iso- Ethyl 77:23 Dimethyl- 91 6.33 butylphthalate 1e Ethyl Isobutyl 16:84 Pentadecane 97 5.89 1f n- Isobutyl43:57 Isododecane 93 6.53 pro- pyl 1g n- Isobutyl 43:57 Isododecane 886.20 pro- pyl 1h Iso- Isobutyl 43:57 Isododecane 90 6.41 butyl 1I Iso-Isobutyl 96:4  Ethylacetate 77 5.46 butyl 1j Iso- Isobutyl  0:100Isododecane 70 6.26 butyl

EXAMPLE 2

Preparation of a mixture of2,2-bis(1-methoxy-1-methylethylperoxy)4-methyl pentane andbis(1-(1-methoxy-1-methylethylperoxy)-1,3-dimethylbutyl) peroxide

To a stirred solution of 50 g of methylisobutyl ketone peroxidecontaining 7.89 wt. % dihydroperoxy-1,3dimethylbutane and 36.84 wt. %bis(1-hydroperoxy-1,3-dimethylbutyl)peroxide in pentadecane was added0.60 g acetic acid. Then 13.73 g 2-methoxypropene were added in 10 min,the reaction temperature being kept at 20° C. by cooling with anice-water bath. The mixture was stirred for 30 min and 1.20 g of aceticacid were added. The mixture was allowed to stand overnight, yielding 65g of product with an active oxygen content of 6.15%. Chemical yield:97%.

EXAMPLE 3

Preparation of 1,1-bis(1-isobutoxyethylperoxy)cyclohexane

To a stirred solution of 30 g of 1,1-dihydroperoxycyclohexane inethylacetate was added 0.4 g p-toluene sulfonic acid. Then 19.6 gisobutyl vinyl ether were added in 10 min, the reaction temperaturebeing kept at 20° C. by cooling with an ice-water bath. The mixture wasstirred for 60 min. The mixture was washed with sodium bicarbonatesolution and dried on MgSO₄. Yield 35 g of product with an active oxygencontent of 6.75% Chemical yield:67%.

EXAMPLE 4

Preparation of 2,2-bis(1-ethoxypropylperoxy)4-methyl pentane

To a stirred solution of 5 g of methyl isobutyl ketone peroxidecontaining 35.7 wt. % bis(1-hydroperoxy-1,3-dimethylbutyl)peroxide inisododecane was added 0.05 g p-toluene sulfonic acid. Then 1.8 g ethylpropenyl ether were added in 10 min, the reaction temperature being keptat 20° C. by cooling with an ice-water bath. The mixture was stirred for20 min at 15° C. The mixture was washed with bicarbonate solution anddried over magnesium sulphate, yielding 5.8 g of product with an activeoxygen content of 5.12% Chemical yield:91%.

EXAMPLE 5

Preparation of a mixture of 2,2-di(1-methoxybutylperoxy)butane anddi(1-(1-methoxybutylperoxy)1-methylpropyl)peroxide.

To a stirred solution of 25 g methylethyl ketone peroxide, containing27.82 wt. % 2,2-bis(hydroperoxy)butane and 14.4 wt. %bis(1-hydroperoxy-1-methylpropyl)peroxide in dimethyl phthalate wasadded 0.86 g p-toluene sulfonic acid monohydrate. Then 21.8 g1,1-dimethoxybutane were added in 16 min, keeping the reactiontemperature at 20° C. by cooling with an ice-water bath. The mixture wasstirred 20 min more at 20° C., washed with bicarbonate solution, anddried over magnesium sulphate, yielding 35.2 g of product with an activeoxygen content of 6.68%. (chemical yield: 90%).

EXAMPLE 6

Curing of unsaturated polyester

The curing performance of peroxides as curing agent for unsaturatedpolyester was determined and compared with tertiary butyl peroxy-2-ethylhexanoate.

A time-temperature curve was measured at 100° C. on compounds containing100 parts of polyester resin, 150 parts of sand as filler, and 1 part ofperoxide. This was carried out according to the method outlined by theSociety of Plastic Institute. 25 g of the compounds were poured into atest tube and a thermocouple was placed through the enclosure at thecentre of the tube. The glass tube was then placed in the oil bathmaintained at a specific test temperature and the time-temperature curvewas measured. From the curve the following parameters were calculated.

Gel time (GT)=time in minutes elapsed between 16.7° C. below and 5.6° C.above the bath temperature.

Time to peak exotherm (TTP)=time elapsed between the start of theexperiment and the moment that the peak temperature is reached. Peakexotherm (PE)=the maximum temperature which is reached. The results areshown in Table 2

TABLE 2 Peroxide Test temp. ° C. GT min. TTP. Min PE ° C. t-butylperoxy-2- 100 0.87 3.4 197 ethyl hexanoate Example 1c 100 2.17 5.57 184Example 1g 100 0.78 3.38 197 Example 1h 100 0.67 3.22 195

EXAMPLE 7

High-solids acrylic resin synthesis

The suitability of the peroxides according to the invention for theproduction of high-solids acrylic resin was determined and compared withtert.butyl peroxy-2-ethyl hexanoate.

Polymerizations were conducted under nitrogen in a jacketed glassreactor equipped with a turbine stirrer, a thermocouple, a refluxcondenser, and an injection inlet. The peroxide initiator was added tothe monomers. This mixture was dosed to the solvent in a stirred vesselvia the laboratory pump at the prescribed temperature in approx. 4hours. The reaction was continued for an additional hour to reduceresidual monomerlinitiator. From the resins obtained the molecularweights, colour, and percentage of solids were determined. Thetemperature was 165° C. The results are shown in Table 3.

TABLE 3 Solids Initiator content Mw Mn Initiator meq/100 g M (%) (g/mol)(g/mol) Disp. Example 1 30 71.0 5400 2700 2.0 t-butyl peroxy-2- 30 74.35400 2900 1.9 ethyl hexanoate

Recipe:

Monomers (in parts by weight)

n-butylacrylate (BA): 40

styrene (STY): 20

2-hydroxyethyl methacrylate (HEMA): 28

methyl methacrylate (MMA): 10

methacrylic acid (MA): 2

Solvesso 100 (S-100): 40 (solvent)

Initiator concentration: 30 meq/100 g monomers Temperature: 165° C.

Molecular weights were determined by gel permeation chromatography usingpolystyrene standards, according to method AR/94.14-1/HPLC obtainablefrom Akzo Nobel. Solids contents were determined by percentage ofnon-volatile matter (0.5 hour at 150° C.).

What is claimed is:
 1. A process for the preparation of a peroxidehaving the formula (I),

wherein n=1 or 2, R₁, R₂, R₄, R₅, and R₆ are independently selected fromthe group consisting of hydrogen, C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl,C₆-C₂₀ aryl, C₇-C₂₀ aralkyl, and C₇-C₂₀ alkaryl, or R₁ and R₂ form aC₃-C₁₂ cycloalkyl group, which groups may include linear or branchedalkyl moieties; and each of R₁, R₂, R₄, R₅, and R₆, may optionally besubstituted with one or more groups selected from hydroxy, alkoxy,linear or branched alkyl, aryloxy, halogen, ester, carboxy, nitrile, andamido, and R₁ and R₂, may form a ring, and R₃ is independently selectedfrom the group consisting of C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀aryl, C₇-C₂₀ aralkyl, and C₇-C₂₀ alkaryl, which groups may includelinear or branched alkyl moieties, and R₃ may optionally be substitutedwith one or more groups selected from hydroxy, alkoxy, linear orbranched alkyl, aryloxy, halogen, ester, carboxy, nitrile, and amido,and any pair of the optionally substituted R₃, R₄, R₅, and R₆, may forma ring, comprising the reaction of the corresponding ketone peroxidewith the formula (II)

 wherein n, R₁, and R₂ have the identified meaning, with an alkyl vinylether with the formula (IIIa) or with an acetal with the formula (IIIb)

wherein R₃, R₄, R₅, and R₆, in the presence of a catalyst.
 2. A processas claimed in claim 1, wherein R₄ is hydrogen.
 3. A process as claimedin claim 1 wherein R₅ and/or R₆ are hydrogen.
 4. A process as claimed inclaim 1 wherein the equivalent amount of the alkyl vinyl ether (IIIa) oracetal (IIIb) is in the range of 1-5 equivalents.
 5. A process asclaimed in claim 1 wherein the ketone peroxide (IIa) is a mixture of theketone peroxide having the formula (IIa),

and of the ketone peroxide with the formula (IIb).


6. A process as claimed in claim 1 wherein the ketone peroxide isderived from methylethyl ketone, methylisopropyl ketone, methylisobumlketone, acetone, cyclohexanone and/or 3,3,5-tnmethylcyclohexanone,preferably from methylisobutyl ketone or methylethyl ketone.
 7. Aprocess as claimed in claim 1 wherein the alkyl vinyl ether (IIIa) isselected from ethyl vinyl ether, isobutyl vinyl ether, propyl vinylether and butyl vinyl ether, preferably from isobutyl vinyl ether, orthe acetal (IIIb) is selected from 2,2-dimethoxypropane,2,2-diethoxypropane, 1,1-dimethoxybutane, 2-propyl-1,3-dioxolane,1,1-dimethoxyethane, 1,1-diethoxyethane, 1,1-diethoxypropane, and1,1-dimethoxycyclohexane.
 8. A peroxide having the formula (I)

wherein n, R₁, R₂, R₃, R₄, R₅, and R₆ have the identified meaning asgiven in any of claims 1 to
 3. 9. A formulation comprising a peroxide asclaimed in claim 8, and a carrier or diluent.
 10. A formulation asclaimed in claim 9, comprising the peroxide in an amount of 1.0-99 wt. %and the carrier or diluent.
 11. A formulation as claimed in claim 9 or10 wherein the carrier or diluent is a solid, liquid or paste.
 12. Aformulation as claimed in any of claims 9 to 10 wherein the liquid is apolar solvent.
 13. A formulation as claimed in any of claims 9 to 10having the form of a dispersion.
 14. A polymerization process whereinmonomers are formed into a polymer by initiating the polymerization ofthe monomers with a peroxide as claimed in claim 8 to form the polymer.15. A process for curing an unsaturated polyester by curing theunsaturated polyester with a peroxide as claimed in claim
 8. 16. Aprocess for the degradation, cross-linking or grafting of a polymer bydegrading, cross-linking or grafting the polymer with a peroxide asclaimed in claim 8.